21790809 has 24 divisors (see below), whose sum is σ = 33276320. Its totient is φ = 14085792.

The previous prime is 21790801. The next prime is 21790841. The reversal of 21790809 is 90809712.

It is a happy number.

It is not a de Polignac number, because 21790809 - 2³ = 21790801 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21790801) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 158989 + ... + 159125.

Almost surely, 2^21790809 is an apocalyptic number.

It is an amenable number.

21790809 is a deficient number, since it is larger than the sum of its proper divisors (11485511).

21790809 is an equidigital number, since it uses as much as digits as its factorization.

21790809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 326 (or 183 counting only the distinct ones).

The product of its (nonzero) digits is 9072, while the sum is 36.

The square root of 21790809 is about 4668.0626602478. The cubic root of 21790809 is about 279.3129797916.

The spelling of 21790809 in words is "twenty-one million, seven hundred ninety thousand, eight hundred nine".